Snowmelt can refreeze at colder eaves and hold water above the normal drainage path. GAF discusses ventilation and leak barriers as parts of prevention
GAF technical bulletin: Ice dams cause and preventative measures.
What this means for your roof
Snowmelt can refreeze at colder eaves and hold water above the normal drainage path. GAF discusses ventilation and leak barriers as parts of prevention. These measures do not make every roof immune to severe ice backup.
A useful question for your contractor
Ask how insulation, air leakage, drainage and roof protection work together.
Ask for the answer to be tied to the actual roof condition and the exact product being installed. Keep the agreed repair or installation detail with your estimate and project photos.
Bulletin revision: February 1, 2021. This is the date of the manufacturer source, not a claim that this website guide existed on that date.
Read GAF: Ice dams cause and preventative measures
This homeowner summary explains the cited bulletin. The complete manufacturer document and current product instructions govern the installation details. A requirement for one manufacturer or product should not be transferred to another without checking.